Question

In development, nervous system (brain, spinal cord, nerve cells) is
А. Ectodermal
B. Endodermal
C. Ectomesodermal
D. Endomesodermal

Answer 1

Hint: Nervous system helps in the control and coordination of the body. It helps to carry information from the outside stimulus to the brain and gives the desired response. It exerts greatest control over the body responsiveness. It is composed of structural and functional units of the nervous system called neurons.

Complete answer:
The inner cell mass of the blastocyst after implantation that is after getting attached to the wall of uterus differentiates into an outer ectoderm, middle mesoderm and inner endoderm. These three layers then develop into tissues that are different tissues, nervous tissue , muscle tissue , epithelial tissues and organs of the embryo such as stomach , brain and much more.

Now let us match this with given options :-
> Ectodermal :- the cell of the ectoderm gives rise to the brain , spinal cord that is nervous tissue. It is the outermost layer so called an ectoderm. It forms pineal gland, epidermis , eyes , nasal epithelium and pituitary gland.

> Endodermal :- the cells of this layer are produced from the inner layer that is endoderm. This layer gives rise to gut , visceral organs , glands of stomach and intestine , tongue , lungs , trachea and bronchi.

> Ectomesodermal :- when a mesoderm is derived from an ectoderm that is an ectodermal layer it is known as ectomesodermal. The cells are always mesenchymal. It is present in primitive type of connective tissue.

> Endomesodermal :- when mesoderm is derived from endoderm that is inner layer of the cells it is called as endomesodermal. This layer mostly give rise to dermis of the skin.

Hence, the correct answer is option (A).

Note: Endometrium secretes a nutrient fluid and its mucosal cells become enlarged with stored nutrients. As the morula enters the uterus, it gets a rich supply of nutrients. Outer peripheral cells enlarge and flatten further. They form trophoblast or trophectoderm. Trophoblast cells secrete a fluid into the interior creating a cavity called blastocoel. The inner cell mass now comes to lie on one side as an embryonal knob. With the formation of blastocoel, morula is converted into blastula.